Catalytic conversion of hydrocarbons



Dec. 4, 1945. D. K. FINL'AYSON CATALYTIC CONVERSION OF HYDROCARBONS 2Sheets-Shee t 1 Filed July 31 1941 WQQ DUNCAN 1a Fl/VLA ysolv" INVENTORBY 6 i ATTORNEY Patented Dec. 4, 1945 S PATENT OFFICE CATALYTICCONVERSION OF HYDBOCARBONS Duncan K. Finlayson, Bronxville, N.

Y., assignor to The M. W. Kellogg Company, Jersey City, N. J acorporation of Delaware application July 31, 1941, Serial N0.'404,766

lclaim.

My invention relates to the catalytic reforming of light distillatehydrocarbons and similar materials. Further, it relates to the catalyticdehydrogenation and aromatization'of aliphatic and naphthenichydrocarbons. More particularly, it comprises an improved unitaryprocess for reacting two or more petroleum naphthas of diflerent Anobject of my invention is to convert light hydrocarbon distillates andsimilar materials into motor fuels of improved quality. Another objectis to convert relatively low octane number naph-" thas. into relativelyhigh octane number aromatic type motor fuels by contacting said naphthasin the vapor phase with dehydrogenating and arov matizing catalysts in areaction zone at elevated temperature and pressure. A further object isthe provision of a method whichpermits more eficient processing ofpetroleum hydrocarbons. An important object of my invention is toprovide a unitary method of reforming two or more differcnt types ofnaphtha. Various other objects, ad-

vantages, and features of the invention will'be readily apparent fromthe following description.

Many different types of naphtha'feed stocks are available for catalyticreforming. The diflerences may be caused by varying geographicalsources, varying processes from which the naphthas have been derived; orvarying treatment to which they have been subjected. Classification ofthe naphthas is difllcult because they are, for the most part, extremelycomplex mixtures of many types of hydrocarbon compounds. However, suchterms as parafllnic, unsaturate, naphthenic, or aromatic as hereinafteremployed in a relative sense are sufllciently definitive for one skilledin the art to apply them to the operation of the present invention. Whenit is desired to process two or more types of naphthas ina singlecatalytic reforming unit, the present practice is to combine these feedsand process the mixture as a .sin8 stream. This is not an entirelysatisfactory procedure since the optimum reaction conditions to whichone type of naphtha should be subjected are seldom the same as theoptimum conditions for another type. These differences in preferredtreatment arise from differences in such p operties as refractorlness,coke forming tendencies, hy-

' drogen producing tendencies, etc. I have discovered that theshort-comings of the usual operation on a simple mixture can besubstantially eliminated by the application of my invention wherein onetype of naphtha is contacted with the catalysts at reaction conditionsin a zone of suiflcient magnitude to bring about a part of the desiredreaction, and another type of naphthais mixed with the now partlyreacted first nap and the mixture contacted with the cat lyst atreaction conditions-in a zone of sufllcient magnitude to complete thereaction of the first naphtha and one typ obtain the same or of arecycled gaseous each of the different types others.

petroleum naphthas at 'bring'about the desired reaction of the secondnaphtha. The invention can be easily applied to the processing of two,three, or more types of naphtha. For the sake of convenience thefollowing examples of the application of my invention have been limitedto cases involving only two types of naphtha.-

Ithas been found in catalytic reforming that some hydrocarbons are morerefractory than For example, predominately parafllnic hydrocarbonmixtures require more severe reaction conditions than hydrocarbonmixtures in orderthat a product of a given octane number be produced. Itis therefore impossible to obtain the required extent of reaction oneach type of hydrocarbon mixture when the usual method of bperation isemployed wherein both typ s are mixed and contacted with the catalysttogether for the entire reaction. The practice of my invention makesitpossible to obtain individual control of the extent of reaction ofeach type of hydrocarbon mixture by contacting alone for a portion ofthe reaction before adding the other type and completing the reaction onthe combined Thusit is possible to even a greater extent of reaction ona more refractory parafllnic naphtha-by contacting it with the catalystin the entire reaction space and contacting a less refractory naphthenicnaphtha with the catalyst in only a portion of said reaction space.

In the dehydrogenation and aromatizatlon of elevated temperatures andpressures over suitable catalysts such as oxides of the sixth group ofadvisable to carry out the reaction in the presence rich in hydrogen inorder to suppress coke formation on the catalyst and for otheradvantageous results. The purity of the hydrogen-containing gas recycleddepends upon the purity and amount of hydrogen produced in the reaction,which in turn depends upon the type of naphtha bein processed. Anadditional factor influencing the purity of the hydrogen-containing gasand thus the purity of the recycled hydrogen is the pressure in thereaction zone-lower pressures resulting in gases richer in hydrogen. Itwill be readily seen that compensation for the tendency of a naphtha toproduce a gas be made by selection of a lower reaction pressure. Theusual method of operation, wherein two or more na hthas are mixed andcontacted with the catalyst throughout the entire. reaction zone, doesnot allow the use of the optimum pressure on of naphtha. This objectionis overcome to a considerable extent by the practice of my inventionwherein a first naphtha which tends. to produce a gas rich in hydrogen rexample, a highly naphthenic naphtha) is predominately 'nap'hthenic theperiodic system, it is often,

product which is preferablywhich is too lean in hydrogen can a contactedwith catalyst in an initial reaction zone at a relatively high pressure,and a second naphtha which tends to produce a gas relatively lean inhydrogen (for example, a highly cracked naphtha) is mixed with the nowpartly reacted first naphtha and the mixture contacted with catalyst ina second reaction Zone maintained at a lower pressure than thatmaintained in sa d 113st zone.

In the catalytic reforming of petroleum naphthas a carbonaceous materialis usually deposited on the catalyst, the amount of said deposit beingproportional to the severity of the operating con-- ditions and theextent of reaction. The necessary removal of the carbonaceous deposit isboth difilcult and expensive, and the amount of the deposit is thereforean important economic consideration. It has been found that-thosenaphthas which are rich in 'unsaturate hydrocarbons, such as crackednaphthas, have a greater tendency to deposit carbonaceous material onthe catalyst than the comparatively saturate hydrocarbons, such asvirgin naphthas. In many instances, the magnitude of this carbonaceousdeposit resulting from the cracked. naphtha is the limiting factor asregards the severity of conditions which is allowable and the extent ofreaction which is feasible in the usual method of operation wherein therelatively unsaturate feed is mixed with the saturate feed and the twocontacted with the catalyst together. This situation is obviated by thepractice of my invention wherein the virgin naphtha alone may becontacted with the catalyst for a portion of the reaction and thecracked naphtha subsequently added, thereby completing the reaction onthe combined streams.

For convenience the present invention will be described in detail withrespect to the catalytic dehydrogenation and aromatization of a virginpetroleum naphtha and an equal amount of cracked petroleum naphthawherein it is desired to subject the cracked naphtha to less extensivereaction conditions than the virgin naphtha. However, it is to beunderstood that the invention is not limited thereto and is applicablegenerally to the field of catalytic reforming of light distillatehydrocarbons and similar materials.

In the accompanying drawings, forming a part of this specification- Fig.1 represents diagrammatically a simplified now-sheet oi my improvedsystem, the catalyst being maintained in fixed beds and regenerated insitu. and

Fig. 2 represents an alternate arrangement in which the catalyst infinely divided form continuously passes through the reaction zones.

Referring to Fig. 1 of the drawings, a virgin naphtha feed is introducedthrough line I by pump 2 into a heating coil 3 in furnace l. A suitableamount of hydrogen-containing gas, preferably a recycle gas derived fromthe convers on products of the reaction, is introduced through line 5,addedto the virgin feed in line I. and passed through heating coil 3therewith. Optionally'the hydrogen-containing gas may be heated in aseparate coil and added to the naphtha subsequent to the heater. Afterbeing vaporized and heated to a suitable temperature in coil 3, themixture of hydrogen and virgin naphtha is passed by line 0 into catalysttower 1' and through the catalyst bed contained therein.

A cracked naphtha feed is introduced through line 8 by pump 0 intoheating coil I. in furnace 4. A suitable portion oi thehydrogen-containing gas may be introduced through line H and added tothe cracked naphtha stream in line I. The hydrogen-containing gas may besuitably proportioned between the virgin and the cracked naphtha streamsby means of valves l2 and I 3, or by closing valve It all oi the gas maybe added to the virgin naphtha stream. After being vaporized and heatedto a suitable temperature in'coil lo the cracked naphtha is passed byline H into catalyst tower I, suitable distributing means I5 beingprovided.

Catalyst tower I is filled with a dehydrogenating and aromatizingcatalyst, for example, molybdenum oxide supported on a'ctivated alumina.The mixture of virgin naphtha and hydrogencontaining gas from line 8 ispassed through tower 7 in contact with the catalyst through an initialzone of suitable size and under other operating conditions adapted tobring about a desired part of the reaction on the virgin naphtha beforemeeting the stream of cracked naphtha from line H. The commingledstreams of cracked naphtha and partly reacted virgin naphtha, togetherwith the hydrogen-containing gas are then passed through the remainderof tower I in contact with the catalyst in a second zone of suitablesize and under other operating conditions adapted to complete thereaction desired on the virgin naphtha stream and adapted to bring aboutthe desired reaction on the cracked naphtha stream. The particularoperating conditions employed in the various zones may suitablycorrespond to those disclosed in co-pending application, Serial No.294,784, filed September 13, 1939.

Operating conditions suitably maintained in the first zone, wherein onlythe virgin naphtha is contacted with the catalyst, are illustrated bythe following example of the conversion of a 42 octane number (C. F. R.M.) East Texas virgin naphtha having an initial boiling point of 250 R,an end point of 400 F., and an A. P. I. gravity of 50:

Temperature-inlet of reactor (line 6)-- Operating conditions suitablymaintained in the second zone, wherein both virgin and cracked naphthaare contacted with the catalyst, are illustrated by the followingexample of the conversion of a 62 octane number cracked naphtha havingan initial boiling point of 220 R, an end point of 400 F., and an A. P.I. gravity of 49:

Temperature-inlet of reactor (line 14)- Temperature-combinedstreams-start of second zon (approx.)--' F Temperature-outlet of reactor(line 16)- F Pressure-lba/sq. in. gage Space velocity-vols. crackednaphtha/hr./vol. catalyst in second zone Hydrogen gas recycle-cu.ft./bbl. cracked naphtha. (In addition to that with virgin naphtha) 2500Length of each reaction periodhours 8 From tower 1 the reaction productsare withways well known in drawn through line it and pass through coolerll into highpressure separator l8. This separator is maintained at suchconditions of temperature and pressure that separation is obtainedbetween the normally gaseous materials and the liquid reaction products.The normally gaseous materials comprise hydrogen and hydrocarbons of oneto three carbon atoms. Preferably the separation is carried out undersuch conditions of temperature and pressure that the normally gaseousmaterials are relatively rich in hydrogen. The liquid reaction productsare withdrawn from separator l8 by line I8 and passed to suitablestabilization or fractionation equipment, not shown. Thehydrogen-containing gas is withdrawn from separator l8 by line 20. Asuitable portion of this gas is recycled by line 2| and compressor 22 tothe distribution valves l2 and I3 for introduction into the naphtha feedstreams as previously described. The portion of the hydrogen-containinggas whichis not desired for recycling is removed from the line 23 forfurther use or processing as desired.

During the course of the reaction a deactivating carbonaceous materialis deposited on the catalyst. This deposit may be removed in many theart-for example, by passing an oxygen-containinggas over the catalyst,provision for such regenerating gas bein made by suitably valved lines24 and 25. The operation or the unit may be made continuous by theprovision of a plurality of reactors, one or more being used forreaction while others are being regenerated, purged, etc.

The reaction or the virgin naphtha in its passage-through tower I isendothermic so that there is a temperature drop in the first zonebetween the inlet of line I and the inlet of the cracked naphtha fromline ll unless heat is supplied from an exterior source. 7 This heat maybe supplied by introducing the cracked naphtha from line ll at atemperature substantially perature dictated by the conversionrequirements of the cracked riap'hthaalone. By thus raising thetemperature or the mixture of virgin and cracked naphthas and thehydrogen-containing ,gas the heat content of the combined streamsbecomes suilicient to permit-the reaction of such mixture without theendothermic'nature of the reaction causing an excessively lowtemperature.

The tendency of a cracked naphtha to produce hydrogen is not so great asthat of a virgin naphtha at substantiall'y the same pressure because ofthe unsaturate nature of the former.

' It may, therefore, be desirable to operate the second zone, in whichthe mixture is reacted, at a somewhat lower pressurethan the first zone.This may be brought about by suitable throttling means inserted betweenthe zones, many methods of carrying out this pressure reduction beingapparent to those skilled in the art. A preferred means of carrying outthe pressure reduction would be to enclose each zone in separate towerswith.suitable valving or throttling means interposed.

The invention may also be carried out in a system in whichthe catalystin finely divided or powdered form passes through the reaction zones. Asimplified fiow sheet of such a system is depicted in Fig. 2. Theoperationof my invention is now described in conjunction with Fig. 2,and forclarity of presentation a typical example is employed in which acracked naphtha is injected into the 'reaction zone subsequent to theinjection of a virgin naphtha stream. The virgin system by valved cedthrough line 28 by naphtha feed is introd pump 21 into heating coil 28in iurnace28. A

suitable amount of hydrogen-containing gas is introduced through line38, added to the virgin feed in line 26 and passed through heating coil28 therewith. After being vaporized and heated to a suitable temperaturein coil 28, the mixture of hydrogen and virgin naphtha is passed by line3| to the base of reactor 32:: where it is Joined by a powderedcatalyst-laden hydrogen-containing gas from line 33.

- ably be a dehydrogenating and aromatizing catapart of the reaction onare relatively low, that lyst, for example, molybdenum oxide supportedon activated alumina. The catalyst, hydrogencontaining gas, and virginnaphtha pass up through reactor 32a, which is a first zone of suitablesize and maintained under other operating conditions adapted to bringabout a desired the virgin naphtha. The proportions of reactor 32a arepreferably .selected so that the upward linear vapor velocities is inthe range of 1 to 25 feet per second, and preferably in the range ofabout 1 to 5 feet per second. By regulating the velocity of the gases inthe reactor the concentration of the catalyst within the reaction zonemay be suitably maintained within the range of about 2 to 25 pounds ofcubic foot of reactor volume, and within the range of about 6 to 16preferably pounds per cubic foot. The catalyst in the reaction zone is a31 and added to the cracked stream in line 3|.

above the tem- 32a and After being vaporized and heated to a suitabletemperature in coil 36, the cracked naphtha is passed by line 38 intoline 39 containing the, stream of catalyst-bearing vapors of the-mixtureof hydrogen-containing gas and partlyreacted virgin naphtha. The streamsof cracked naphtha and partly reacted virgin naphtha together with thehydrogen-containing gas and the powdered catalyst are passed reactionzone 32b, which zone is of suitable size and maintained under otheroperating conditions adapted to complete the reaction desired on thevirgin naphtha stream and adapted to bring about the desired reaction on"the cracked naphtha stream. The particular operating conditionsemployed in the various zones may suitably correspond to those disclosedin co-pending application, Serial No. 348,605, filed July 31, 1940.

The various reaction by a constricted area such as line 38 as shown, inwhich case there will be no internal recircula zones may be separatedzone 32b and first zone 32a. The reaction zones 32!; may be incorporatedin a single reactor without the constriction 38, and the vapors fromline as may be injected with the use of suitable distribution meansbetween the reaction zones. In the latter case, the powdered cats-'-lyst may be maintained in a "fluidized bed with considerable internalrecycle of catalyst. The second reaction zone is preferably of greatercross sectional area than the first zone in 'order to compensate for thegreater volume of vapors passing This catalyst may suitabout catalystper commingled tion of the fluidized catalyst between secondtherethrough. As in the case oi. the fixed-bed operation, the inventionas carried out in Fig. 2 may be operated with different conditions oftemperature and pressure in the two reaction zones.

From reaction zone 32b the reaction products and catalyst are withdrawnby line 40 to suitable catalyst separating means 4|. .This separatingmeans may comprise cyclone separators, Cottrell precipitators, or anyapparatus of like function, all of which are well known in the art. Fromcatalyst separating means 4| the reaction products are withdrawn throughline 42 and pass through cooler 43 into high pressure separator 44 fromwhich liquid reaction products are with drawn by line 45 and normallygaseous materials are withdrawn by line 46.

The used catalyst in separating means 41 is partly deactivated by adeposit of carbonaceous material. This deposit may be removed bywithdrawing the used catalyst; from separating means 4! by pump 41 andpassing said catalyst along with oxygen-containing gas from line 48through regenerator 49 in which the necessary combustion takes place.The regenerated catalyst suspended in the regeneration fiue gas thenpasses to catalyst separating means 50, the regeneration flue gas beingremoved by line ll.

It may be desirable to pretreat the regenerated catalyst with ahydrogen-containing gas prior to using said catalyst in the reactionzone. This is suitably carried out by removing th regenerated catalystfrom catalyst-separating means II by means of pump 52 and passing saidcatalyst along with a hydrogen-containing gas from line I! throughcatalyst pretreatment zone 84 which is maintained under the necessaryoperating conditions. From pretreatment zone 54 the catalyst-laden,hydrogen-containing gas is passed through line 33 to th reaction zone.By suitable piping means, not shown, a portion of the stream in line 33may be injected into line 38 along with or close to the inlet of line38. The hydrogencontaining gas in line 53 which is used for the catalystpretreatment is preferably a recycle gas derived from the reactionproducts. The recycle be practiced with suitable .difierent ways andthat gas is suitably proportioned among the virgin naphtha stream (line30 to line 24), the cracked naphtha stream (line 31 to line 34), and thecatalyst pretreatment (line I! to pump II). It may be found desirable topass all of the recycle gas to the catalyst pretreatment zone 84. Thenet product hydrogen-containing gas is withdrawn through valved line II.

For purposes of clarity the operation of my invention has been describedin concrete examples with particular reference to the addition of acracked naphtha to a reaction zone at a point subsequent to the partialreaction of a virgin naphtha. In certain instances, however, the Pointsof introduction of the two naphtha streams may be reversed, in whichcase the initial portion of the reaction zone is maintained underpreferred conditions for partially converting the cracked naphtha, andthe subsequent portion of the reaction zone is maintained underpreferred conditions for converting the combined streams. It is furtherapparent that the invention may modification in many it may be appliedto naphthas and similar materials of many diiferent types as heretoforedescribed.

I claim:

The method of reforming by catalytic dehydrogenation two difierent typesof naphtha, said types being based on substantial differences inoperating conditions required to effect a given amount ofdehydrogenation which comprises passing the first type or naphtha alongwith a finely divided or powdered catalyst through an initial reactionzone of sufiicient volume to bring about part of the desired reaction,admixing the second type of naphtha with the partly reactedcatalyst-bearing first naphtha, and passing the commingled naphthasthrough a second zone at a pressure lower than that maintained in thefirst zone of sufficient volume to complete the reaction of said firstnaphtha and simultaneously bring about the desired reaction of saidsecond naphtha.

DUNCAN K. FINLAYSON.

